Since World War 2 (1939-1945) pushed the need for more air-transportable anti-armor solutions to meet the enemy's growing stable of heavily-armored tanks, world powers sought to develop such weapons. Beyond basic shoulder-fired solutions there stood a requirement for a effective lightweight tracked armored vehicle offering the mobility of a standard combat tank with the hard-hitting firepower of an Anti-Tank (AT) field gun. The Allies delivered several combat systems in this mold - the American M22 "Locust" being one example - and work on even more useful types continued into the post-war years - the principle enemy now having become the Soviet Union.
The British airborne paratrooper proved his mettle in actions throughout the war but his reach was limited by how far he could advance at speed since the element of surprise was his true unwritten weapon. Paratroopers were deployed as light infantry simply due to the fact that they would be assaulting from transport aircraft and could only carry so much. Glider elements added another tactical advantage in that they could deliver heavier payloads - namely JEEPs, supplies and artillery - but still there was no better solution in dealing with the new generation of enemy tank. Therefore the British Army began looking into a modern "air-transportable" vehicle in the 1950s which lead to the FV4401 "Contentious" appearing during the early part of the next decade.
"Project Prodigal" was enacted to develop the next generation of British armored vehicles to overtake family lines still in use - some developed even prior to World War 2. One of the intended assets to come from this initiative was a light combat system mounting a suitable AT gun to help airborne troopers stave off elimination from an enemy tank entering the battle. With such a system, troopers could stand a chance at holding ground until the primary force could arrive. Additionally, such a portable combat vehicle added a tactical advantage and could be deployed nearly anywhere the European battlefields required.
The resulting FV4401 design was as compact and lightweight as possible. It lacked a covered superstructure to save on weight though this left the operating crew (of two, driver and commander/gunner) exposed to the elements and general battlefield dangers. The main gun armament became an Ordnance QF 20-pounder system (84mm) which gave good penetration value at range - the primary enemy model being the T-54/55 Main Battle Tank (MBT) of the Soviet Army. This main gun, the same as fitted to the British Army "Centurion" MBT - was fixed to the superstructure with only limited traversal and elevation functions - the fixed nature of the weapon did away with a complex and heavy turret mounting system which helped to maintain the required dimensions of the vehicle. The Contentious held a running length of 8.5 meters and a width of 3.1 meters.
With its turret-less design, the FV4401 also showcased a very low profile from any angle, making it a harder target to engage by the enemy with any level of success at far-off ranges. However this also meant that the driver would be mostly responsible for aligning the bow of the vehicle to the direction of fire for the commander/gunner. The vehicle was powered by a Rolls-Royce B range gasoline-fueled engine, the powerpack and overall design of the vehicle estimated to make about 500 miles on road. A hydraulic suspension system was fitted for cross-country travel and many components of the chassis were simply taken from the earlier "Comet" combat tank to expedite development. The suspension allowed individual control over the height of each track system and gave the hull the ability to angle itself forward over the bow or backward - the latter elevating the main gun in the process.
The partially-completed prototype was pushed into testing with some crude accommodations in place. It was eventually up-gunned with the British 105mm L7 rifled main gun in concert to the Centurion itself being up-gunned from its original 20-pounder. As many as three prototypes are said to have been completed prior to the end of testing - which did not see the Contentious adopted for service. Additional work saw the product fitted with 2 x 120mm recoilless rifles (similar in battlefield scope to the American M50 "Ontos" vehicle) but this initiative was not furthered into a production form either.
An example of the Contentious prototype is on display at the Bovington Tank Museum of England.